We use a procedure to extract valuable information regarding the p-wave halos in 8B and 11Be from the measured nuclear asymptotic normalization coefficients. With this procedure, we evaluate the probabilities of valence particle being outside the binding potential, which are 0.31 ± 0.03 for the 8B ground state and 0.59 ± 0.06 for the 11 Be first excited state. More than 50% probability outside the binding potential means that the 11 Be first excited state has a typical p-wave neutron halo. The rms radii are obtained to be 3.9 ± 0.2 fm for the valence proton in the 8B ground state and to be 6.5 ± 0.3 fm for the valence neutron in the 11Be first excited state.The probabilities of the valence particle being in the non-classical region are extracted to be 0.41 ± 0.04 and 0.46 ± 0.05 for the 8B ground state and the 11 Be first excited state, respectively. The results demonstrate that although hindered by the effects of Coulomb and/or centrifugal barriers, their valence particle wave function still penetrates substantially into the classically forbidden region.